HVAC systems include a variety of different components, or units, to provide a complete heating and/or cooling cycle. These units may include heat pumps, furnaces, compressors, fans, heat exchangers, and air handlers. Each unit typically has a control device to receive control signals to operate the unit, possibly in conjunction with other units of the system, to condition a space by heating or cooling the space to a desired temperature. The control devices of the units are generally inter-connected to a thermostat that sends electronic signals to the various control devices based on a comparison between a desired temperature for the conditioned space and the actual temperature of the space.
Current methods of analyzing a failure or malfunction of the HVAC system to troubleshoot a problem with the HVAC system typically include taking measurements of different control signals of various units of the HVAC system to determine, for example, the presence and/or magnitude of an electric potential between two points in the system, typically between terminals of control units of the different HVAC components in the system. Those measurements are then manually compared to a previously prepared wiring diagram and/or troubleshooting chart to determine the operational status of the system.
Several aspects of the current methods of analysis make troubleshooting a time consuming and economically inefficient process. First, wiring charts must be prepared for the specific HVAC system to be serviced, taking into consideration each of the various units used in the HVAC system. Because of the variety in type, size and manufacturers of units that might be used in an HVAC system, wiring diagrams must often be custom made for each HVAC system. Furthermore, as various components of the HVAC system are replaced over time, terminal configurations may change such that a previously prepared wiring diagram for a once-standard system no longer accurately depicts the as-modified system.
Second, even after the wiring diagram is prepared for a particular HVAC system, the wiring diagram must reflect the state of each control signal (i.e., energized or de-energized), depending on the operation of the HVAC system that is to be performed. For example, the control signals sent from a thermostat are different depending on whether the temperature in a conditioned space is warmer or lower than a pre-established set point. Thus, different terminals of the controls of the various units in the HVAC system may be energized or de-energized to send control signals for unit operation depending on the specific operation desired of the HVAC system. For each HVAC system, a different wiring diagram may need to be produced for every possible operation of the HVAC system, including every variation of heating, cooling, and fan speeds, by way of example only. Accordingly, even after a technician measures the control signals in a malfunctioning system and manually compares them to a wiring diagram, he must then make sure he has the correct wiring diagram for the particular HVAC system operation during which the measurements were taken.
Because technician skill varies widely, human error can also play a role in whether or not an HVAC system is properly analyzed and affect the time needed to subsequently troubleshoot a problem system.
Therefore, what is needed is an analysis tool that automatically generates a wiring diagram in view of known components in an HVAC system and generates and shows expected states in HVAC system operation to a technician. In addition, what is needed is an analysis tool that can detect and measure the status of various controls of the units in the HVAC system and automatically use those measured signals to compare expected HVAC system behavior for a given operation with the actual behavior of the HVAC system under consideration.